1. Field of the Invention
This invention is directed to the field of automotive sound systems of the type used in cars, trucks and the like and more particularly to direct and reflected sound imaging using planar magnetic transducers for the source of sound generation. The transducers are mounted and oriented within a vehicle such that separate stereo or surround sound stages are created for each passenger while cross talk or cross interference is reduced when compared with conventional sound systems.
2. Description of the Related Art
Conventional automotive speaker layouts use left and right transducers that are placed at opposite sides of an automotive vehicle. This results in unequal sound arrival amplitude and time cues such that there is little or no stereo image perceived by a passenger. A center channel will move the image to the center of the vehicle, but the same limitations apply and there is limited ability to project sound around the passengers. Digital time delays have been employed to move the image to one side of the vehicle, but this only works for one passenger. The sound quality in the remainder of the vehicle is degraded. Limited alternative approaches have used standard voice coil center speaker(s) or DSP delays with standard voice coil speakers in different locations, however, both approaches have limitations in sound or imaging quality over a full frequency range.
Directional transducers have well known desirable characteristics but have traditionally had limited implementation in vehicles due to lower efficiency, high cutoff frequencies, and mounting limitations. Small flat panel transducers used as a dipole have difficulty achieving sufficient acoustic output at moderate distances below 400 Hz. This is a problem because the speakers cannot interface directly with a subwoofer. Using an interior portion of a vehicle as an infinite baffle or ported enclosure reduces the low frequency limitation and small flat panel transducers can interface directly with a subwoofer.
Hence there is currently no high quality solution for an improved stereo image over a full range for individual sound in an automotive vehicle. Also there is a need for a high quality, small, flat panel transducer that can be mounted within a vehicle to achieve low frequency response while having output levels high enough for automotive listening.